InvalidCastException in NumericUpDown

[nsrahmad]

I am learning so I don't know If I am doing something wrong or it is a bug.

Describe the bug
NumericUpDown shows System.InvalidCastException: Unable to convert object '89.6' of type 'System.Double' to type 'System.Nullable'1[System.Decimal]'.
I am using a class implementing IValueConverter to convert the value.

To Reproduce
Project has just a few lines changed from template:
https://github.com/nsrahmad/7GUI-Avalonia/tree/master/TemperatureConverter

Expected behavior
No errors. The error contains the right answer, so conversion is happening.

Screenshots

Desktop (please complete the following information):

• OS: Windows 10
• Version 11.0.0-preview4

Additional context
Add any other context about the problem here.

[timunie]

@nsrahmad I think we had a breaking change here in 11.0. The reason is, that double has rounding issues where decimal doesn't have these problems. This is important if you work with percentage or currency values.

I see two options for you:

1. use decimal in the bound Property
2. use a Converter

See also: #5981

[maxkatz6]

Not related but you also have a typo here

[nsrahmad]

@maxkatz6 Thanks.

@timunie Using decimal sort of worked. But I started to get StackOverflowException if I try to change the value with mouse wheel 3 or 4 times.

It took me some time to remove FormatString to uncover rounding issues in my converter. So trying to convert 1 celsius to fahrenheit would give:

> Console.WriteLine((1M * (9M / 5M)) + 32M);
33.8

But trying to convert back 33.8 to celsius would give:

> Console.WriteLine((33.8M - 32M) * (5M / 9M));
1.0000000000000000000000000001

I had to call decimal.Round on the result to fix it. Thank you for your help.